My cats like them a lot for mid-afternoon treats. The cats have become very good at getting at the treats, so there's not as much exercise involved as I would have hoped. Nonetheless, the sounds of my putting treats into the balls wakes them up from their naps and brings them to the kitchen aquiver in anticipation. Cats are sometimes like circling sharks.
I think all cats love to chase things and what's better than a ball shaped object that moves with the least little tap of their paw. And as if the movement weren't enough, the scent of a cat treat you can put inside will keep your kitty's attention -- watch as he gets ready to pounce and attack!
This product is a good value and my adult cat learned what he needed to do to get the treats very quickly. The only hard thing is getting the ball open if you don't have strong hands to pry the two halves apart.